Evidence for Predicted Level Crossings inπ̃h92⊗ν̃i132Bands in Very Neutron-Deficient, Doubly Odd T1 Isotopes

Isomeric transitions, of E3, M2, and E1/M2 character, depopulating pi-tildeh/sub 9/2/xnu-tildei/sub 13/2/ bands in /sup 186,188,190/Tl, respectively, have been found with use of ..gamma..-ray spectroscopic techniques. The changes in multipolarity reflect successive changes in the bandhead spin values corresponding to level crossings within the pi-tildeh/sub 9/2/xnu-tildei/sub 13/2/ system. These crossings were predicted in the framework of the two-quasiparticle plus rotor model and interpreted as a direct consequence of the depletion of the i/sub 13/2/ shell.